What does the buffy coat layer in a blood sample primarily consist of?

The buffy coat layer in a blood sample is a thin layer that forms between the plasma and the red blood cells after centrifugation. It primarily consists of white blood cells (leukocytes) and platelets (thrombocytes). This layer is crucial for various hematological assessments because it contains the components of the immune system, which are essential for fighting infections and responding to injuries. The presence of platelets in the buffy coat is significant as they play a key role in blood clotting and wound healing.

In contrast, red blood cells are found in the lower layer of the centrifuged sample, while plasma is the clear liquid portion that remains at the top. Plasma contains water, electrolytes, proteins, and waste products but does not include the cellular components present in the buffy coat. Serum is similar to plasma but lacks clotting factors; thus, it is not part of the buffy coat composition. Fat is not a component of this layer either, as it would not typically separate into a distinct layer in a standard blood sample.